ES6 Classes
Classes provide a cleaner syntax for creating objects and dealing with inheritance in JavaScript.
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📋 Copy Modern JavaScript Class with Private Fields Snippet
// Modern Class with Private Fields & Static Factory
class UserAccount {
#passwordHash; // True private field enforced by engine
constructor(username, passwordHash) {
this.username = username;
this.#passwordHash = passwordHash;
}
static createDefault(username) {
return new UserAccount(username, "default_hash");
}
verify(hash) {
return this.#passwordHash === hash;
}
}⚠️ 5 Fatal Traps & JavaScript Pitfalls
Trap #1: Losing this Context When Passing Methods as Callbacks
Passing
button.addEventListener("click", user.verify) detaches the method from the instance, leaving this undefined. Bind the method or use an arrow function.Trap #2: Accessing this Before super() in Subclasses
In a subclass constructor, referencing
this before calling super() throws an immediate ReferenceError: Must call super constructor before accessing this.Trap #3: JavaScript Classes Are NOT Hoisted
Unlike function declarations, classes are in the Temporal Dead Zone until execution reaches them. Instantiating a class before its declaration throws a
ReferenceError.Trap #4: Private Field Syntax (#field) Outside Class Error
Attempting to access
user.#passwordHash outside the class declaration is a syntax error caught at parse-time.Trap #5: Classes Are Syntactic Sugar Over Prototypes
Underneath the hood, JavaScript classes still use prototype chains. Methods are attached to
Class.prototype, not copied onto each instance.💬 Frequently Asked Questions
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